/Engine/Source/Runtime/MovieScene/Public/Evaluation/MovieSceneEvaluationTrack.h
When not 'None', setting an evaluation group indicates that all tracks with similar groups and priorities should be grouped together at runtime. Named groups can be optionally flushed immediately at runtime by calling IMovieSceneTemplateGenerator::FlushGroupImmediately with the appropriate group.
void SetEvaluationGroup ( [FName](API\Runtime\Core\UObject\FName) InEvaluationGroup )